Apparatus for automatic track registration

Claim 1

An automatic track searching device for a magnetic video tape recorder/reproducer comprising magnetic tape supply and take-up reels, tape transport means operatively associated with said reels, a guide drum provided with a slot and helically encircled at a determinable wrap angle by the magnetic tape, at least one video head rotating in said guide drum and scanning said tape through said slot in diagonal video tracks, and a stationary track finding magnetic head in said guide drum within said wrap angle and having a magnetic gap flush with the guide drum surface and having a length equal to the width and a direction perpendicular to the direction of said video tracks; said track finding head scanning about the center of the magnetic tape in longitudinal direction to produce an amplitude-modulated high-frequency output voltage, the peaks of said output voltage being a measure of the actual position of said video tracks; a threshold amplifier, said output voltage, after being amplified and rectified, being applied to said threshold amplifier, said threshold amplifier having a threshold voltage which is lower than the peak of said output voltage and higher than said peak voltage multiplied by the difference of said video track width and the interspace between said video tracks and divided by said video track width; a phase comparator, the output of said threshold amplifier being connected to said phase comparator and being phase compared with the rated position signals of said rotating video head to form an error signal; said error signal being applied to said tape transport means to readjust the relative positions of said tape and said rotating video head so as to minimize tracking error between said video head and said video tracks.